Conduit string



March 3, 1964 w. A. DAVIS CONDUIT STRING FILL-UP DEVICE 2 Sheets-Sheet 1 Filed Nov. 14. 1960 INV EN TOR.

7 March 3, 1964 w, DAVls 3,123,517

CONDUIT STRING FILL-UP DEVICE Filed Nov. 14, 1960 2 Sheets-Sheet 2 Wi/l/om A. flow:

INVENTOR.

A TZ'OR/VE KI United States Patent Filed Nov. 14-, 196i), Ser. No. 69,136 7 Claims. (Cl. 166-224) This invention relates to an apparatus for filling conduit strings, such as casing for example, as it is run into a fluid-containing well bore, and more specifically to a casing collar or shoe provided with a back pressure valve and a fluid bypass about the back pressure valve where flow in the bypass is controlled by a flow control element.

In running conduit strings, such as easing, into a well filled with fluid, it has been customary for many years to place on the lower end of such conduit string a check valve or closure of some kind which would prevent the fluid standing in the well from flowing into the pipe. Without such a closure, the fluid entering the conduit string could have suflicient force that it would rise through the conduit string and flow up to and overflow on the drill rig floor. This overflow is prevented by the use of such closure and leaves the interior of the conduit string filled with air which gives it much greater buoyancy and avoids the necessity for as much lifting force to suspend the pipe on the surface. However, when the pipe reaches a considerable depth, the hydraulic pressure on the exterior of the air-filled pipe becomes so great that it is apt to collapse the pipe. In order to counter this tendency, it is the practice to partially fill the pipe with liquid each time that it goes deeper into the fluid standing in the well. It is desirable that the pipe always be left partially empty to assist in the floating operation but the filling will go on as the pipe is lowered so that the lower portion of the pipe, which is subject to the greatest hydraulic force from the outside, will not be collapsed.

At first the filling of the pipe was eflected by introducing fluid at the upper end of the pipe after each stand was coupled on and lowered; however, this took considerable time and necessitated leaving the upper end of the pipe hanging and open while an operator with a hose injected a fluid, usually drilling mud, into the upper end of the pipe. In order to avoid this necessity, devices were originated that would leave a small opening or orifice through which fluid in the well bore would be allowed to enter the lower end of the pipe at a constant rate calculated to be sufiicient to keep the pipe partially filled with fluid as it is lowered into the well. These devices filled the pipe but not to any given depth and did not allow unobstructed flow of cement or well fluids down wardly through the conduit string.

Substantial hydraulic pressures are created when conduit strings are lowered into a well bore due to the close clearances between the conduit string and the well bore and the usual viscous nature of the mud fluids in the well being contained therebetween. This, of course, results in great pressure being developed as the conduit string is lowered into the well, which forces the viscous muds deeply into the pores and crevices of the surrounding formations. It has been found that such resultant penetration of the mud fluids into the oil or gas production area will entirely plug these formations to the extent that the oil and gas can not escape into the well. This results in the failure of wells to produce successfully. It is clearly seen that removing fluid from the well bore at the lower end of the casing string will relieve such pressure creating viscous mud fluids and is an advantage obtained by filling from the lower end over filling the conduit string at its upper end with a fluid which may or may not be the same as that in the well bore.

3,123,517 Patented Mar. 3, 1954 "ice Many of the heretofore known devices utilized a relatively large back pressure cementing valve secured at the lower extremity of the conduit string to permit unobstructed downward flow of cement and at some point above this valve provided a plurality of ports through which mud could flow from the well bore directly into the conduit string. These bypass ports were adapted to be opened and closed by a pressure actuated valve member. The valve would be forced open by a given total diflerential in pressure between the well fluid and the fluid within the conduit string and closed when this pressure differential was reduced to some desired value such that the well fluid stood within the conduit string to a desired height. The valves in such devices suflered from many ditficulties due to their mechanical construction including reciprocating piston-like valve elements and springs. Some of the difliculties were created by surges in the well fluid as the casing was lowered. These fluid surges in an upward direction opened the valve with considerable force and therefore could easily damage it. When the pressure diiferential across the valve unit decreased suddenly, such as when the conduit string ceased to be lowered, a downward surge of fluid in the conduit string occurred which, of course, closed the Valve assembly with considerable force and thereby tended to damage it. Thus, the ditliculty with these valves was that the flow through the bypass port was controlled by a valve having mechanical elements directly subject to the total diflerential in pressure between the well bore and conduit string. Thus, the valve was opened and closed with considerable force by surges in fluid presure. Such operation could severely damage the valve operative elements due to the repeated poundings produced by fluid surges and thereby render the filling device inoperative.

Another type of device was developed to avoid the use of such mechanical bypass controlling valve elements that could be damaged by the surges in well fluid. This valve utilized a flexible orifice type resilient member across the lower portion of the conduit string. The resilient orifice member regulated the rate of the fluid flowing therethrough into the conduit string to fill it as it was lowered into the well bore. Some of these type devices utilized orifice valves which would be closed in response to excessive velocities of fluid flowing upwardly therethrough. Other types of this device utilize orifice valves allowing flow in two directions. This latter ori fice valve had the form of a resilient disc positioned across the conduit string at its lower end with a small axial opening therethrough which increased in diameter as the diflerential pressure across it increased. Thus, as a length of conduit string was lowered and the pressure below the resilient apertured member increased, the opening in the disc increased responsively to the pressure increased thereby permitting a greater volume of fluid to enter the casing.

These types of devices utilizing rubber orifice members provide greater advantages than those of the first group in that they do not have such a great tendency to be damaged by surges in the well fluid occurring when the conduit string is lowered into the well bore, but they have disadvantages. One such disadvantage arises whenever it is necessary for the well operator to circulate fluids down through the conduit string into the well bore because the orifice restricts both upward and downward fluid flow. Complicated valve assemblies were developed to permit circulation of fluid downwardly in the conduit string in such orifice devices. Another disadvantage results in that no back pressure valve can be used to seal the end of the casing against gas blowo-uts. Still another disadvantage exists that the full pressure differential between the fluid in the well bore and that in the conduit string could be applied to the resilient orifice member. Thus, the resilient member had to be made sufliciently strong to withstand such pressures and hence lost some of its sensitivity in regulating the rate of the upward flow of fluid into the conduit string.

Thus, the type of well fill-up device that would be most desirable is one wherein:

(l) The flow of fluid upwardly into the conduit stream to fill it is regulated by a resilient flow control member which cannot be damaged by surges in fluid flowing through it in either direction and which is so positioned that the total pressure differential between the well fluid and the fluid within the conduit string is never exerted upon it;

(2) A back pressure valve is provided which at all times substantially closes the conduit string against upward flow in the event of a gas blowout or the like; and

(3) The flow of well fluid or cement downwardly through the device is substantially unobstructed while the upward flow of well fluid filling the pipe may be effectively controlled by resilient valve elements for properly filling the conduit string or, if desired, completely shut off. Resilient valve means to control such filling should not be damaged by repeated operations and reversals of fluid flow therethrough.

It is therefore an object of the present invention to provide a novel fill-up device for conduit strings that controllably fills the string with well fluid as it is lowered into a well bore having fluid therein and which is so constructed that cementing operations may be carried out in the usual fashion upon the conduit string being set to. its final position within the well bore.

Another object is to provide a fill-up device for a conduit string that permits a substantially unobstructed downward flow of well fluid or cement therethrough while the upward flow of fluid to fill the conduit string is restricted and the restricted flow is regulated by a resilient flow control member which cannot be damaged by surges in the well fluid arising from sources in the well bore and/or the interior of the conduit string.

Another further object is to provide a fill up device in which the portions of the device that allow a well fluid to. flow upward therethrough to fill the conduit string may be sealed oil and the remainder of the device used as a standard cementing or back pressure valved floating shoe or collar.

Yet another object is to provide a fill-up device that may be made completely drillable yet is simple to construct and strong in construction so that it may withstand the well pressures and yet is effective in normal use.

Another object is to provide a fill up device for con duit strings in which the total fluid pressure diflerential between the well bore and conduit string cannot be applied to the resilient flow control means that regulate the filling of the conduit string, and fluid can flow through such means in either direction without damaging it.

A further object is to provide a fill-up device having a common fluid inlet port, both for the purposes of filling the conduit string with fluid as it is lowered into the well bore and through which mud or cement may be pumped downwardly, thereby permitting the use of a single mud filter and/or surge breaker thereacross.

These and other objects will become more apparent when read in conjunction with the following detailed description and the attached drawing or a preferred illustrative embodiment of the present invention, wherein:

FIG. 1 is a vertical section of the lower part of a conduit string wherein the fillup device is illustrated as a float collar and the fluid filter and surge breaker is illustrated as being embodied in a conventional guide or cementing shoe;

FIG. 2 is. a partial section similar to FIG. 1 but showing the fill-up device with the portion of the device that permits restricted upward flow of fluid sealed oil;

FIG. 3 is a section taken along line 3-3 of FIG. 1;

FIG. 4 is a section taken along line t4 of FIG. 1;

FIG. 5 is a section taken along line 5-5 of FIG. 1; and

FIG. 6 is an exploded enlarged partial perspective illustrating part of a plastic conduit forming the restricted bypass passageway in the body of the fill-up device and an apertured resilient disc that controls fiuid flow therethrough.

The objects of the present invention are achieved by a fill-up device as specifically illustrated in the drawings and described hereafter which is comprised of a tubular member adapted to form part of the conduit string and having means tiereon for attachment to an adjacent conduit string section. Said member is provided with a fluid port whereby the conduit string and the well bore are in fluid communication. The tubular member is provided with a valve seat thereon fixed with respect to it and interposed between the fluid port and the interior of the conduit string. A valve member that it movable longitudinally out of and into engagement with the seat is provided to prevent upward flow of fluid through said seat and into the conduit string. This valve arrangement provides a cementing or back pressure valve. The tubular member is also provided with one or more restricted passageways through which fluid can flow between the fluid port and the interior of the conduit string while bypassing said valve member. llhis passageway provides for a restricted flow of fluid upwardly into the conduit string from the well bore, which flow fills the conduit string. A fluid control means consisting of an apertured and slitted resilient valve member is positioned across this restricted passageway adjacent is terminus at the interior of the conduit string to vary the fluid flowing therethrough in either direction responsiv-ely to the pressure differential thereacross and especially to regulate the rate at which the well fluid fills the pipe between a maximum and minimum rate of flow. The maximum rate of flow is determined by the flow through the restricted passageway and the minimum rate of flow is determined by the opening in the resilient valve member. The variation of rate of flow between these rates is responsive to the pressure differential across the resilient valve member. A valve means is provided which is movable mechanically to a position across the restricted passageway to close same so that fluid can only pass downwardly through the first said valve member from within the conduit string into the well bore. It may be found desirable in some cases to provide a fluid filter and surge breaker across the fluid port to prevent debris from entering the passageways and reducing fluid surges. The filter and surge breaker is provided with parts disruptable by a downward flow of fluid so that an unrestricted downward flow of fluid is obtained therethrough.

For the purpose of description of the present invention, the fill-up device will be described as incorporated into a float collar positioned in the conduit string at a point closely adjacent its lower end and the fluid filter and surge breaker will be described as incorporated Within a cementing or guide shoe which is secured to the lower end of the conduit string.

Referring to FIG. 1, the fill-up device is illustrated in the form of a float collar it). The float collar ill is comprised of a tubular assembly ill adapted to form a part or" the conduit string 7.2 and having an internally threaded box 13 at its upper extremity and an externally threaded pin 14 at its lower extremity. A flowway 15 is provided axially through the tubular member and extends partially of its length and terminates at its lower end in an enlarged area 16. The enlarged area 16 communicates with a fluid port 17 at the lower extremity of the conduit string and thereby fluid communication is established between the enlarged area 16 and the well bore. A cementing orback pressure valve is provided in the tubular member and is comprised of a resilient valve seat 13 secured in the tubular assembly 11 at the juncture of the flowway l and the enlarged area 16. A valve member 19 is reciprocably mounted on guide 22 within a spider 29 in the tubular assembly 11 and is adapted to move longitudinally into and out of engagement with said seat 18 to restrict upward flow of fluid into the remainder of the conduit string. Resilient means such as spring 21 is provided to urge the valve member into engagement with the valve seat. The spider 24 is, of course, as seen in FIG. 4, provided with a plurality of openings 23 therethrough to permit substantially unobstructed flow of fluid between the fluid port 17 and the enlarged area 16. Other types of back pressure valves may be used as is apparent to one skilled in the art.

it can be seen that with this arrangement of valve member 19 and seat 18 as a back pressure valve, the flow of fluid upwardly through the seat 18 is prevented while downward flow of fluid therethrough can be obtained substantially unobstructed and unrestricted.

Provided in tubular assembly 11 are one or more restricted passageways 24 communicating between the enlarged area 16 and the flowway so that fluid can flow between the interior of the conduit string and the fluid port 17, bypassing the back pressure valve. The restricted passageways 24 are dimensioned so as to permit only such rate of flow therethrough that each length of conduit string can be filled up to a given depth as it is lowered into the well bore at its maximum rate of descent. Thus, the restricted passageways 24 determine the maximum rate of flow of well fluid into the conduit string to fill it under the maximum rate of descent of the conduit string downwardly into the well bore. This is an important advantage since only a limited upward flow of fluid can result even when a gas blowout occurs.

It is evident that when the conduit string is lowered into the well bore at lesser rates of descent than such maxrate, there would be a tendency for the well fluid to flow through the pasagcway at a rate greater than required to partially fill the conduit string. To regulate the flow through the passageways 24'. during periods of descent less than the maximum rate, a flow control means 25 is positioned across the restricted passageways 24 and secured adjacent their terminus at flowway 15 in tubular assembly ill. The flow control means takes the form of a flexible apertured resilient slitted valve member.

Referring to FIG. 6, the apertured resilient valve member takes the form of a resilient disc 2H6 having an aperture or axial opening 27 therethrough. 'Disc 26 is divided into two portions 29 and as by a slit 2% formed diametrically thereacross. The aperture 27 is dimensioned so that fluid can flow therethrough up to a predetermined rate determined by a pressure differential across the disc when the conduit string is stationary, into the conduit string partially filling it without deflecting portions 29 and 3th The height of rise of the well fluid in the conduit string, usually viscous drilling mud, is determined by the pressure drop in the restricted passageways Z4, and the flow restriction of the aperture 25' so that the mud will not, for all practical purposes, fill the conduit string above a given depth even when it is stationary. Thus, by using the restricted passageways, the valve means for controlling filling can be arranged so that it does not need to close and form a fluid tight seal. This allows the use of a simple valve element, without the mechanical parts formerly required to form a fluid tight seal when the valve was closed.

Under conditions where the conduit string is lowered at a rate less than the maximum rate of descent, the rate of flow of fluid through the passageways 24 is varied by the flow control means 25 to partially fill the conduit string. This variation is due to the pressure differential across the disc 26 increasing sufficiently above the mentioned predetermined diflerential so that the portions 29 and 30 of the disc 26 adjacent the slit 2%; are flexed and deflected to permit fluid flow therethrough proportional to the differential across the disc up to the maximum rate of flow obtainable through the restricted passageways 24. The portions 29 and 30 can be repeatedly deflected without damage as they are merely flexed out of their original positions rather than stretched as is the case of a resilient disc with a flow controlling aperture.

Thus, the maximum rate of flow into the conduit string is determined by the restricted passageways 24, the minimum rate of flow is determined by the size of the aperture .27 in the disc 26, and the rates of flow therebetween are determined by the pressure differential across the disc, deflecting the portions 29 and 3th of the disc adjacent the slit 2%. In this manner the filling of the conduit string with well fluid is controlled so that as a practical matter it never rises above a given depth partially filling the conduit string and cannot overflow onto the drilling floor and will thereby always provide for some buoyancy.

By positioning the flow control means 25 adjacent the interior terminus of the bypass passageway 24 at the flowway l5, excessive pressure differentials, such as can exist between the well fluid and the fluid within the interior of the conduit string, cannot be applied across the resilient flow control means because of the pressure dropping and flow controlling action of the restricted passageways 24. Excessive surges of fluid cannot be applied upwardly from the well bore against this element because of the action of the restricted passageways 24, nor can excessive pressure differentials and fluid flows be applied downwardly through the flow control means 25. An excessive downward surge of fluid, such as occurs when the conduit string is suddenly stopped in its descent, will not pass through the flow control means 25 but rather will open the valve member 19 and pass downwardly therethrough substantially unrestricted. This is an advantage because the flow control means need only withstand a moderate pressure differential thereacross rather than the full pressure diflerential between the well bore and conduit string and hence can be made more sensitive in its functioning than the resilient orifice valve heretofore mentioned.

It has been found with this arrangement that the flow control means 25 may be an apertured resilient member which can pass fluid equally in either of two directions and which never needs to completely prevent all fluid flow; i.e. an aperture is provided through the means wherethrough fluid can flow at all times. Thus, reversals in fluid flows cannot damage it.

Because fluids can flow downwardly as Well as upwardly through the passageways 214 into the enlarged area 16 and thence to the fluid port 17 in the conduit string, an important advantage is achieved in that such flows will clean the fill-up device and fluid filter each time the descent of the conduit string in the well bore is interrupted.

The bypass flow through the restricted passageways 24 may be terminated by a sleeve 31 which is reciprocally mounted within the flowway 15. A tubular liner 32 is fixed within the inner walls of the flowway 15 to facilitate reciprocation of sleeve 31 and also to cooperate with the sleeve in sealing off the passageways 2d. The seal is provided by a pair of spaced apart annular grooves 33 and 34- about the outer periphery of sleeve 31 wherein are positioned sealing means such as O-rings 35 and 36. Thus, it can be seen that when the sleeve 31 is in its lowermost position the passageways 24 are effectively closed by an O-ring sealing above and below each of them. fluid pressure from the passageways 2.4 is applied between the O-rings equally and therefore there is no tendency to move sleeve '31 upwardly. The sleeve 31 has an outwardly or radially extending flange portion 37 formed on its uppermost end, which is spaced apart from the walls of the tubular assembly 11 so that there is no possibility of it being pressure operable. Thus, the sleeve is not displaced by fluid pressures either in its upper or lower positions. The sleeve is held in its upper position by frangible means which in the present embodiment may be provided by shear pins '38 extending through the walls of tubular member 11 into openings in the flange 37 of sleeve 31.

Thus, it is apparent that the sleeve may be moved mechanically downward by some convenient means. When in its lower position the fill-up device will function as a back pressure valve and withstand pressures comparable to the ordinary back pressure valves. This means for moving the sleeve 31 may be provided by a bottom plug which can be pumped downwardly through the conduit string until it seats upon the flanged portion 37 of sleeve 31. This can be seen in FIG. 2. This bottom plug 3 is a resilient plug provided with a relatively thin resilient membrane 55i covering an axial openin ll therethrough. It can be pumped downwardly through a conduit string until it reaches a restriction and upon an increase in pum pressure the membrane ruptures and allows fluid to proceed down through it. In this manner a bottom plug may be used to shear the frangible means and cause dowi ward movement of the sleeve thereby closing the passageways ii l. The pump pressure then can be increased to rupture the membrane at the top of the plug and thereby permit unobstructed fluid flow downwardly therethrough. The fill-up device can then be used as a standard cementing shoe or back pressure valve assembly. Other means of moving the sleeve 31 may be used which do not permit fluid flows upwardly or downwardly thereafter. The usual cementing plug can be such means. if the membrane is not ruptured, it will also serve as a cementing plug. As seen in FlG. 2, upon closing the passageways 24 by such means, spring 21 will close the valve member 19 when hydrostatic pressure is relieved thereacross and thereby preventing any further upward and downward flow of fluid through the fill-up device.

Reference is now had to FIG. 1 wherein there is shown a fluid filter and surge breaking means incorporated in a guide shoe. The guide shoe 42 is comprised of a tubular assembly 43' having means at one end in the form of an internally threaded box 44 so that the shoe may be secured to the end of the conduit string and provided with a flowway 45 therethrough to provide for fluid communication between the interior of the conduit string and the well bore through fluid port 17. The fluid filter and surge breaking means 36 is interposed between the conduit string and the fluid port as previously described. The fluid filter and surge breaking means is provided by an annular resilient member 4'7 having one or more axial openings 48 therethrough and adapted to be secured Within guide shoe 42. A plurality of parts 49 are provided in the annular member 47 which are disruptable by fluid being pumped downwardly through the conduit string so as to provide a greater opening in such member through which the pumped fluid can pass downwardly substantially unobstructed. The disruptable parts 49 are provided by a plurality of recessed areas fill in the upper surface 51 of the annular member 47 and are disposed about the central opening therethrough. The lower surface 56 is continuous throughout the member 47 about opening This results in the parts being disruptable more easily by a downward flow of fluid than by an upward fluid flow.

A reinforcing web 52, preferably a woven fabric, extends medially through the disc and about the central openings and the recessed areas. The reinforcing reduces the tendency of the opening d? to be distended when subjected to fluid pressure differentials across the member 47. The extent of the opening 48 through the member 47 should be suiiicient to allow upward flow of well fluid therethrough somewhat in excess of the maximum flow permitted through the restricted passageways 24 in the fill-up devic By providing a plurality of openings 48 it is, of course, obvious that the member 47 will act as a fiuid filter to prevent debris or large cakes of mud from passing into the fill-up device and possibly clogging the V 8 restricted passageways 24 and also to reduce fluid surges. The reinforcing web 52 provides another function besides preventing distension of the er %7 about the opening 8 therethrough in that it stiffens the member so that fluid may be pumped downwardly at moderate rates and yet develops a suflicient pressure differential across the member 47 to rupture the disruptable parts 49 and increase the extent of the opening theretlirough. This is most desirable when it is desirable to circulate mud through the conduit string into the well bore. Such instance may occur when a bridging in the well bore prevents the conduit string from being lowered. In such cases, freely circulating fluids assist in removing the bridging and thus freeing the conduit string. However, the flow of fluid downwardly through the conduit string should be substantially unobstructed. Additionally, it is desirable to have substantially unobstructed downward flow of fluid when cement is pumped downwardly through the conduit string to fill the annulus between the conduit string and well bore when the casing is cemented therein. These are important features and advantages of the present invention.

The construction of the fill-up device and also of the fluid filter and surge breaker is such that the internal parts of these devices be constructed from completely drillable materials. This is important where such an arrangement is used to cement a casing in place; and after it is sealed, a cutter or drill bit is passed down through it to open a bore through the cemented area so that further drilling may be effected. in such instances, the sleeve 31 may be constructed of a drillable material, such as aluminum. The spider 2b, guide 152 and valve member 19 may be constructed of reinforced plastics, such as Bakelite, the spring 22 of brass. The seat 18 and the liner 32 may be constructed of a resilient material, such as neoprene. The materials wherein are formed the passageways 24 are provided most conveniently by easily drillable cement 55. Thus, it can be seen that the passageways 24 can be conveniently formed in the fill-up device by the use of plastic tubing 53 of the proper size positioned therein to provide communication between the iiowway l5 and the enlarged area 16 and filling the remaining spaces with cement 55. Likewise, the guide shoe l2 seen in FIG. 1 may be similarly formed. The annular resilient member 47 may be positioned within a mold in the tubular member 43 and the remainder of the space filled with cement In this manner, the devices according to the present invention may be constructed of completely drillable materials.

Thus, there has been herein provided a fill-up device that is adapted to partially fill a conduit string with Well fluid as it is lowered and in which the filling flow is regulated by an apertured resilient flow control member which cannot be damaged by surges in fluid flowing through it in either direction and which is so positioned that it never is subiect to the total pressure (inferential between the well fluid and the fluid within the conduit string. Additionally, a back pressure or cementing valve is provided which at all times substantially closes the conduit string against upward flow of lid in the event of a gas blowout or like, but permits substantially unobstructed downward flow of well fluid therethrough. If desired, the flow of fluid filling the conduit string can be completely shut off whenever esired by the use of a bottom plug and the remainder of the device used as a cementing shoe. Additionally, all fluid flow through the device may be terminated by moving the sleeve across the passageway with a cementing plug. Since all fluid flow through the fill-up device passes through a common fluid port, a single fluid filter and surge breaker can be positioned thereacross. The fluid filter and surge breaker is arranged so that unrestricted downward flow therethrough can be obtained when desired.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages 9 which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. A fill-up device for a conduit string which is adapted to be lowered within a well bore having fluid therein comprising a tubular member adapted to form part of the conduit string, said member provided with a fluid port whereby said conduit string and the well bore are in fluid communication; said tubular member having a valve seat therein fixed with respect thereto and interposed between the fluid port and the conduit string, a valve member movable longitudinally into and out of engagement with said seat to restrict upward flow of fluid into said conduit string, said tubular member provided with a restricted passageway communicating between the conduit string and the interior of the device below the valve member through which fluid can flow and thereby bypassing said valve member, and pressure differential actuated flow control means positioned across said restricted passageway having a minimum constant opening for fluid flow therethrough, and said control means being responsive to increases in pressure differential to increase said opening and to decreases in pressure differential to decrease said opening toward said minimum opening as a limit.

2. A fill-up device as in claim 1 wherein said flow control means comprises a flexible resilient disc secured across the restricted passageway which has an axial opening therethrough and is slit diametrically whereby fluid can flow through the opening up to a predetermined differential in pressure across the disc without deflecting portions of the member adjacent the slit, above which pressure the portions of the disc adjacent the slit are deflected to permit fluid flow therethrough proportional to the pressure differential across the disc up to the maximum fluid flow obtainable through said restricted passageway.

3. A fill-up device as in claim 1 wherein said flow control means comprises a flexible resilient member secured across the restricted passageway and provided with an opening therethrough that is in alignment with the flow axis of said passageway, the resilient member being slit parallel to the axis of said opening whereby fluid can flow through the opening up to a predetermined differential in pressure across the resilient member without deflecting portions of the member adjacent the slit, above which pressure differential the portions of the resilient member adjacent said slit are deflected to permit fluid flows therethrough proportional to the pressure diiferential across the disc up to the maximum fluid flow obtainable through said restricted passageway.

4. A fill-up device for a conduit string which is adapted to be lowered within a well bore having fluid therein comprising a tubular member adapted to form part of the conduit string, said member provided with a fluid port whereby the well bore and the conduit string are in fluid communication, back pressure valve means interposed between said fluid port and said conduit string to restrict upward flow of fluid into said conduit string, said tubular member provided with a restricted passageway communicating between the conduit string and the interior of the device below the valve member through which fluid can flow and thereby bypassing the back pressure valve means, flow control means positioned across said restricted passageway to vary the fluid flow therethrough responsively to the pressure differential across such flow control means, a valve means movable to a position across said restricted passageway to close said passageway, and a fluid filter and surge breaking means interposed between said restricted passageway and the fluid port, said last mentioned means comprising an annular resilient member having an axial opening therethrough and relatively stronger and relatively weaker parts, said relatively weaker parts being rupturable by fluid being pumped downwardly through said conduit string to provide a greater aggregate opening in such member through which the pumped fluid can pass.

5. A fill-up device as in claim 4 wherein said fluid filter and surge breaking means comprises a resilient annular disc having a centrally located opening therethrough and provided with relatively weaker parts rupturable by fluid pumped downwardly through said conduit string to provide a greater aggregate opening therein through which the pumped fluid can pass, said rupturable parts being comprised of a plurality of recessed areas in the upper surface of said disc and relatively stronger parts having a reinforcing web extending medially through the disc and about the central opening and the recessed areas, said web being discontinuous across said opening and recessed areas.

6. A fluid filter and surge breaking means for filtering fluids passing therethrough and to reduce surges of such fluids comprising an annular resilient disc having a centrally located opening therethrough and provided with relatively weaker parts rupturable by fluid pressure to provide a greater aggregate opening therein through which fluids can flow, said rupturable parts being comprised of a plurality of recessed areas in one surface of said disc and relatively stronger parts having a reinforcing web extending medially through the disc and about the central opening and recessed areas, said web being discontinuous across said opening and recessed areas.

7. A fill-up device for a conduit string which is adapted to be lowered within a well bore having fluid therein comprising a tubular member adapted to form part of the conduit string, said member provided with a fluid port whereby the well bore and the conduit string are in fluid communication, back pressure valve means interposed between said fluid port and said conduit string to restrict upward flow of fluid into said conduit string, said tubular member provided with a restricted passageway communicating between the conduit string and the interior of the device below the valve member through which fluid can flow and thereby bypassing the back pressure valve means, flow control means positioned across the restricted passageway to vary fluid flow therethrough responsively to the pressure differential across such flow control means, a valve means movable to a position across said restricted passageway to close said passageway, and a fluid filter and surge breaking means interposed between said restricted passageway and the fluid port.

References Cited in the file of this patent UNITED STATES PATENTS 1,659,478 Black Feb. 14, 1928 1,745,304 Lemex Jan. 28, 1930 1,788,358 Goerg Jan. 6, 1931 2,200,922 Heigis May 14, 1940 2,515,073 Binnall et a1 July 11, 1950 2,593,315 Kraft Apr. 15, 1952 2,629,444 ODonnell Feb. 24, 1953 2,735,498 Muse Feb. 21, 1956 2,792,896 Moosman May 21, 1957 2,799,349 Clark July 16, 1957 2,874,785 Muse Feb. 24, 1959 2,973,006 Nelson Feb. 28, 1961 3,007,527 Nelson Nov. 7, 1961 

1. A FILL-UP DEVICE FOR A CONDUIT STRING WHICH IS ADAPTED TO BE LOWERED WITHIN A WELL BORE HAVING FLUID THEREIN COMPRISING A TUBULAR MEMBER ADAPTED TO FORM PART OF THE CONDUIT STRING, SAID MEMBER PROVIDED WITH A FLUID PORT WHEREBY SAID CONDUIT STRING AND THE WELL BORE ARE IN FLUID COMMUNICATION; SAID TUBULAR MEMBER HAVING A VALVE SEAT THEREIN FIXED WITH RESPECT THERETO AND INTERPOSED BETWEEN THE FLUID PORT AND THE CONDUIT STRING, A VALVE MEMBER MOVABLE LONGITUDINALLY INTO AND OUT OF ENGAGEMENT WITH SAID SEAT TO RESTRICT UPWARD FLOW OF FLUID INTO SAID CONDUIT STRING, SAID TUBULAR MEMBER PROVIDED WITH A RESTRICTED PASSAGEWAY COMMUNICATING BETWEEN THE CONDUIT STRING AND THE INTERIOR OF THE DEVICE BELOW THE VALVE MEMBER THROUGH WHICH FLUID CAN FLOW AND THEREBY BYPASSING SAID VALVE CHAMBER, AND PRESSURE DIFFERENTIAL ACTUATED FLOW CONTROL MEANS POSITIONED ACROSS SAID RESTRICTED PASSAGEWAY HAVING A MINIMUM CONSTANT OPENING FOR FLUID FLOW THERETHROUGH, AND SAID CONTROL MEANS BEING RESPONSIVE TO INCREASES IN PRESSURE DIFFERENTIAL TO INCREASE SAID OPENING AND TO DECREASES IN PRESSURE DIFFERENTIAL TO DE- 